It is only recently that it has become possible to formulate liquid detergent compositions containing solid, water soluble peroxygen bleaches. Such detergent compositions are described for instance in EP 0 294 904.
Under normal circumstances, the chemical stability of said peroxygen compound in such liquid detergents is satisfying, thus providing the product with good storage stability characteristics.
However, some products have shown a certain instability of the peroxygen compound, which creates a problem in terms of a sufficient storage stability for an adequate shelf life of these products.
The cause for this peroxygen instability has now been identified as a contamination of the product by transition metal traces which catalyze the decomposition of the peroxygen compound in the composition.
The contamination of the product by transition metal traces is an important problem which cannot be avoided in normal industrial practice; indeed, it has been discovered that some of the raw materials used for the manufacture of the product, are themselves carrying transition metals, at trace levels.
Further, while manufacturing, shipping, handling or stocking the product, accidental contamination may occur because of corroded pipes or containers.
A solution to this problem has been proposed in co-pending European patent application 90 20 0315, which describes aqueous liquid detergent composition containing a peroxygen bleach, wherein the peroxygen bleach is protected against decomposition due to transition metals by an efficient amount of hydroxyethylidene 1,1 disphosphonic acid (HEDP). In these compositions, the peroxygen compound is efficiently stabilized, but a new problem has been encountered in that HEDP tends to form large aggregates in the presence of calcium, which may precipitate. It is believed that this precipitation phenomenon may have somewhat of a detrimental effect on the whiteness maintenance of fabrics washed with HEDP-containing detergent compositions.
Also newly encountered is the fact that the use of HEDP in liquid detergent compositions appears to interfere with the stability in the finished product of enzymes which can be used in detergent compositions.
Of course, these problems can be overcome in an obvious way, e.g., by adding an enzyme stabilizing system and an anti-redeposition agent, or by compromising on the level of HEDP which is used.
The object of the invention is, as an alternative, to provide for a liquid detergent compositions which contains a solid water-soluble peroxygen bleach, which further contains a compound protecting said bleaches from decomposition due to transition metals, wherein said compound is as efficient as HEDP in protecting the bleach, but wherein said compound does not involve any risk of precipitation in the presence of calcium. It is another object of the present invention to provide a liquid detergent composition wherein said compound does not interfere with the enzyme's stability in the finished product.